This invention relates to a face mask used for diving or the other purposes.
Conventional face masks have a lens frame, a pair of buckles mounted on transversely opposite ends of the lens frame and a headband turning around the respective buckles so that a peripheral length of the headband may be adjusted. The headband made of a suitable flexible elastic material such as urethane rubber wherein band guides are used so that the end portions may be stabilized and prevented from obstructing a mask wearer s movement. The headband is formed with a plurality of engagement teeth arranged intermittently in a longitudinal direction of the headband so that any one of the engagement teeth may be engaged with the buckles to adjust a peripheral length of the headband.
In the conventional face masks used for diving or the other purposes as mentioned above, each of the band guides is formed with a first guide opening through which the end portion of the head band is guided from the backside toward the front of the face mask and a second guide opening through which the same end portion is guided from the front toward the backside of the headband after this end portion has been turned around the associated buckle. The guide openings have cross-sections dimensioned to be considerably larger than a cross-section of the headband so that the end portion of the headband may be easily guided through these guide openings. When it is desired to adjust the peripheral length of the headband, the most suitable one of the engagement teeth is brought in engagement with the associated buckle as the headband is moved through the first guide opening of the band guide in a back-and-forth direction of the headband. However, the headband made of silicone rubber or the like is so flexible that the headband may be often unstable within the first guide opening during adjustment of the headband""s peripheral length. Specifically, the engagement tooth may be forcibly brought in contact with a peripheral edge of the first guide opening and thereby obstruct smooth movement of the headband in the back-and-forth direction.
It is an object of this invention to improve a face mask used for diving or the other purposes so that the headband can be smoothly moved through the band guides in the back-and-forth direction to adjust the peripheral length of the headband.
According to this invention, there is provided a face mask comprising a lens frame, buckles mounted on transversely opposite extremities of the lens frame, a headband having longitudinally opposite end portions respectively turning around the buckles so that a peripheral length of the headband is adjusted, and band guides carried by the headband so as to guide the headband passing therethrough.
This invention further comprises the headband made of a flexible elastic plastic and the longitudinally opposite end portions thereof respectively having transversely opposite side edges extending in parallel to a longitudinal direction of the headband, a width of the headband between the side edges as well as a thickness of the headband measured along the side edges being substantially uniform, the end portions being formed on transversely middle zones of respective inner surfaces thereof destined to come in contact with a mask wearer""s head with a plurality of engagement teeth arranged intermittently in a longitudinal direction of the end portions each projecting from one of the inner surfaces and having a front surface gently sloping toward a pointed distal end of one of the end portions in the longitudinal direction and a rear surface abruptly sloping in an opposite direction. Each of the buckles acts upon any one of the engagement teeth under a spring-biasing effect to enable the peripheral length of the headband to be adjusted. Each of the band guides has a first guide opening through which the associated one of the end portions is guided from a backside toward a front of the face mask and a second guide opening through which the end portion is guided from the front toward the backside of the face mask after the end portion has been turned around the associated one of the buckles. Both the first guide opening and the second guide opening have a width corresponding to a width of the headband and a height corresponding to a thickness of the headband. The first guide opening is formed with a first guide area adapted to guide transversely opposite lateral zones the end portion extending along its respective side edges and a second guide area being contiguous to the first guide area and allowing the engagement teeth. The first guide area has a width and a height dimensioned to allow the lateral zones extending along the side edges of the end portion to be slidably moved as the end portion is moved in a back-and-forth direction of the face mask. The second guide area has a width and a height respectively dimensioned to be larger than a width and a height of the engagement teeth so that the engagement teeth may freely pass the guide area. The second guide opening has a height substantially same as or slightly larger than the thickness of the end portion and smaller than a sum of the thickness of the end portion and the height of the engagement teeth so as to prevent the end portion passing therethrough from unintentionally moving and simultaneously to prevent the end portion from coming off from the associated one of the engagement teeth.
This invention includes the following embodiments A plurality of the engagement teeth are provided substantially at a regular spacing in the longitudinal direction of the headband and a dimension of the second guide opening in the longitudinal direction corresponds to the regular spacing.